Modular orthopaedic implant apparatus

ABSTRACT

A trial implant kit includes a plurality of intermediate components and a plurality of inner components. Each of the plurality of intermediate components has a uniform inner surface, although at least two of the plurality of intermediate components having distinct outer surfaces. Each of the distinct outer surfaces is configured to engage one of a plurality of acetabular shell component geometries. Each of the plurality of inner components has a uniform outer surface portion and a bearing surface, the uniform outer surface portion configured to be received by the uniform inner surface of any of plurality of intermediate components. The bearing surface is configured to engage a femoral head. At least two of plurality of inner components having distinct bearing surface configurations.

This application is a continuation of co-pending application Ser. No.11/172,719, filed on Jul. 1, 2005, which in turn is a continuation ofco-pending application Ser. No. 10/319,293, filed on Dec. 13, 2002 (nowU.S. Pat. No. 6,926,740). The disclosures of each of theabove-identified patent applications and patent are herein totallyincorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to prosthetic orthopaedicimplants, and more particularly, to methods and apparatus for implantingmodular orthopaedic implants.

BACKGROUND OF THE INVENTION

Many orthopaedic procedures involve the implantation of prostheticdevices to replace badly damaged or diseased bone tissue. Commonorthopaedic procedures that involve prosthetic devices include total orpartial hip, knee and shoulder replacement. For example, a hipreplacement often involves a prosthetic femoral implant. The femoralimplant usually includes a rigid stem that is secured within the naturalfemur bone tissue. The femoral implant further includes a rounded headthat is received by, and may pivot within, a natural or artificial hipsocket. Knee replacement is somewhat similar, and typically includes oneor more implants that have both bearing surfaces and stems.

Total hip replacement procedures typically involve the implantation oftwo main component systems: the femoral component (as discussed above)and an acetabular component. The femoral component is anchored withinthe existing femur and includes a head that replaces the natural hipjoint femoral head. The acetabular component is secured within theacetabulum of the patient and serves as a bearing surface for thefemoral component.

Many acetabular cups include an outer shell component and an innerliner. The outer shell component has an outer dimension configured tofit within the acetabulum of the patient. The outer shell is typicallyformed from a high strength alloy, such as a titanium alloy, in order towithstand the pressures exerted on the hip joint during normalactivities. The inner liner is configured to tightly fit within theacetabular outer shell component. The inner liner serves as the bearingsurface for the femoral head. Accordingly, the inner liner is typicallyconstructed of a polymeric material, such as for example, polyethylene.Inner liners may also be constructed of cobalt chrome or ceramicmaterial.

The acetabular component of hip replacement includes a number of sizingand shape considerations. In particular, the outer diameter of the outershell is configured to be received by the patient's acetabulum. Whilethe acetabulum may be reamed and otherwise prepared to receive the outershell, it is still necessary to provide multiple sizes of outer shellsto accommodate the varied anatomies of different patients. In additionto the outer diameter of the outer shell, the inner diameter/geometry ofthe inner liner must be configured to receive the femoral head(prosthetic or otherwise) and allow a suitable range of motion. Theinner diameter and geometry of the inner liner can often define 10-15different styles.

Typically, the ultimate determination of which outer shells size andwhich inner liner style to use occurs during surgery. In particular, thesurgeon usually first performs a trialing procedure in which one or moreprosthetic devices are temporarily implanted. The trial devices areevaluated and then the final prosthetic device(s) is selected based onthe evaluation of the trial devices.

During the trialing process, the surgeon assesses the acetabulum and thefemoral head and attempts to select the correct combination of outershell size and inner liner style. The outer shell is typically selectedbased on the geometry of the acetabulum identified by the surgeon. Aninner liner must thereafter be selected. The inner liners are availablein different sizes and styles. As discussed above, the size of the innerliner ultimately depends on the size of the femoral head. Differentliner styles depend on patient geometry and can affect the range ofmotion. Examples of known liner styles include neutral, 10°,lateralized, and lipped. Each is appropriate for a particular situation.

Accordingly, in order to select the appropriate components for theacetabular implant, the surgeon implants trial components on a trial anderror basis until a suitable combination of outer shell size and innerliner style provides acceptable results. To this end, surgeons must haveavailable to them outer shells of various sizes and corresponding trialinner components of different styles and sizes. Moreover, in order toprovide maximum flexibility, all possible styles and sizes of innerliners should be available for every possible size of outer shellcomponent.

It can be readily be appreciated that providing inner liners having allof the possible configurations for each of the different size outershell components can require a large number of trial components. Forexample, if there are six outer shell sizes and thirteen inner linerconfigurations, then up to seventy-eight inner liner trial componentsmust be provided to the surgeon, thirteen styles for each of six outershell sizes. Providing such a quantity of inner liner trial componentsin addition to six outer shell sizes is both costly and inconvenient tomanipulate in the surgical environment.

One prior art patent, U.S. Pat. No. 5,879,401 to Besemer et al., whichis incorporated herein by reference, teaches an acetabular trial systemthat in theory can reduce the number of trial liner components that arenecessary to cover various outer shell sizes and inner liner styles. Tothis end, U.S. Pat. No. 5,879,401 teaches the use of outer shellcomponents that have uniform inner diameters. Because the inner diameterof the outer shell is uniform regardless of its outer diameter, only oneset of inner liners is necessary.

One drawback of such a design is that it requires the outer shells tohave widely varying thicknesses. In particular, because the innerdiameter of the outer shell remains the same while the outer diametervaries, the outer shell thickness must vary accordingly. In the case ofthe largest diameter outer shell, the thickness of the outer shell couldwell approach 16-20 mm in thickness. While such a design is possible, ithas a number of drawbacks. One drawback relates to the use of finalouter shell components in the trial reductions of the joint.

More specifically, because the outer shell may typically be selectedprior to the trial reduction of the joint, surgeons often elect toimplant the final outer shell, and not the trial outer shell, prior toperforming the trial reduction using the trial inner liner. To permitthe flexibility of using either final outer shell or the trial outershell during trial reduction, the trial outer shell and the final outershell must be substantially identical in dimensions. Moreover, if thisflexibility is to be provided using the method of U.S. Pat. No.5,879,401, then the final outer shell must, like the trial outer shell,be available in varying thicknesses in order to maintain the constantinner diameter. Thus, in the case of the largest outer shell sizes, thefinal outer shell can also require a thickness approaching 20 mm.However, normal outer shells have a thickness of on the order of 5 mm-8mm.

It is undesirable to have such thick outer shells because thick outershells require the use of correspondingly thinner inner bearing or linerdevices. Thinner bearings or liners are undesirable because jointlongevity increases as a function of liner thickness. In particular,because the liner serves as the bearing surface for the humeral head, athicker liner will provide a bearing surface that can withstand greaterwear. As a consequence, it is desirable to provide the final liner withlarger thickness. Thus, if excess thickness is used for the outer shell,that excess thickness represents thickness that could have been used toincrease the liner thickness and thus the longevity of the joint.

Thus, there are a number of drawbacks to varying the thickness of theouter shell component to accommodate various inner liner trials.

Accordingly, there is a need for a modular acetabular trial system andmethod that provides flexibility of outer shell sizes and inner linerstyles with a reduced number of components, and which optionally allowthe surgeon to employ final outer shell components during the trialreduction.

SUMMARY OF THE PRESENT INVENTION

The present invention addresses the above needs, as well as others, byproviding a trial acetabular kit and associated method that employs aplurality of intermediate spacers configured to be received into theouter shell component. The intermediate spacers have a uniform innerdiameter, but an outer diameter that corresponds to one of a pluralityof outer shell sizes. The intermediate component allows for a single setof inner liners to be used with each of a plurality of sizes of outershell components. Moreover, the intermediate spacers allow the outershell to have a desired thickness that does not vary widely from size tosize. In this manner, the trial outer shells may readily have the samedimensions as the final outer shell.

A first embodiment of the invention is a trial implant kit that includesa plurality of intermediate components and a plurality of innercomponents. Each of the plurality of intermediate components has auniform inner surface, although at least two of the plurality ofintermediate components having distinct outer surfaces. Each of thedistinct outer surfaces is configured to engage one of a plurality ofacetabular shell component geometries. Each of the plurality of innercomponents has a uniform outer surface portion and a bearing surface,the uniform outer surface portion configured to be received by theuniform inner surface of any of plurality of intermediate components.The bearing surface is configured to engage a femoral head. At least twoof plurality of inner components having distinct bearing surfaceconfigurations.

Preferably, but not necessarily, the trial kit further includes aplurality of acetabular outer shell components.

A second embodiment of the invention is a method of implanting anacetabular component that includes disposing an intermediate componentwithin an acetabular shell component, the intermediate componentdefining a cavity having a first average diameter; The method furtherincludes disposing a first inner component within the intermediatecomponent, the first inner component having a first of a plurality ofbearing surface configurations, the first inner component configured tobe received in the cavity of the intermediate component.

The advantages of the present invention may suitably have application inother orthopaedic implant devices. In particular, the use of anintermediate liner having a uniform inner geometry to act as aninterface between various outer pieces and various inner pieces couldhave application in knee replacement, among others.

The above described features and advantages, as well as others, willbecome more readily apparent to those of ordinary skill in the art byreference to the following detailed description and accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective exploded view of a modular trial acetabularassembly according to the present invention;

FIG. 2 shows an exemplary kit generated in accordance with the presentinvention;

FIGS. 3 a, 3 b and 3 c show a first exemplary modular trial acetabularassembly according to the present invention;

FIGS. 4 a, 4 b and 4 c show a second exemplary modular trial acetabularassembly according to the present invention; and

FIGS. 5 a, 5 b and 5 c show a method of implanting an exemplary modulartrial acetabular assembly according to the present invention.

DETAILED DESCRIPTION

FIG. 1 shows an exploded perspective view of an exemplary modularacetabular trial 10 according to the present invention. The modularacetabular trial 10 is generally configured to be received in theacetabulum of a patient. The modular acetabular trial 10 is furtherconfigured to receive a femoral head, not shown, but which would beknown in the art.

The components of the modular acetabular trial 10 are used, in whole orin part, as trial implants to ascertain the appropriate size and styleof acetabular cup that will be finally implanted. In particular, thesurgeon may use the components of the modular acetabular trial 10,either as a unit or as subcombinations, to determine the outer shelldiameter and the inner liner style of the final acetabular cup implant.

The modular acetabular trial 10 includes an outer shell 12, anintermediate component 14 and an inner liner component 16. The outershell 12 includes a rounded outer surface 20, which is substantiallyhemispherical, but may vary from a true hemisphere, depending on theapplication. The outer surface 20 interfaces with and secures to theacetabulum of a patient. The average diameter of the outer shell 20 willtypically range from on the order of 68 mm to 80 mm, depending on theanatomy of the patient. The outer shell 12 further includes an innersurface 22 that has a shape substantially similar to the outer surface20, although with a smaller diameter. In most embodiments, the innersurface 22 has a diameter that is 10 mm to 16 mm smaller than that ofthe outer surface 20. As a consequence, the outer shell 12 has athickness of about 5 mm to 8 mm.

The outer shell 12 is typically constructed of stainless steel for usein trial applications. However, as will be discussed below, a trialouter shell need not always be used. In particular, a surgeon may electto implant the final outer shell if the proper size of the outer surfacemay be determined without a trial implant. If the outer shell 12 is thefinal implant, the outer shell 12 will be constructed of a higherhardness alloy, such as a titanium alloy. For example, the outer shell12 may be constructed of Ti-6Al-4V.

The outer shell 12 further includes a threaded bore 24 for receiving athreaded fastener, not shown, that secures the intermediate component 14to the outer shell 12. (See also FIGS. 3 and 4). A substantiallycircular rim 26 is defined at the substantially circular edges of theouter surface 20 and the inner surface 22. The substantially circularrim 26 includes a plurality of small, substantial semi-circulardepressions 28 that function as receptacles for complimentary featureson the intermediate component 14, discussed further below.

Referring now to the intermediate component 14, the intermediatecomponent 14 is in the form of a substantially hemispherical shelldefining a cavity 27. The intermediate component 14 includes an outersurface 29, an inner surface 30, and a substantially circular rim 32.The outer surface 29 has a size and shape adapted to be received by theouter shell 12. In particular, the outer surface 29 of the intermediatecomponent 14 is approximately the same size and shape as the innersurface 22 of the outer shell 12. The average diameter of the outersurface 29 is thus dictated by the size of the inner surface 22 of theouter shell 12. As a consequence, because the outer shell 12 can vary indiameter by about 12 mm to accommodate the anatomies of differentpatients, the diameter of the outer surface 29 of the intermediatecomponent 14 will likewise vary by about 12 mm. For example, the outersurface 29 may suitably vary in size from about 52 mm to about 64 mm.

The inner surface 30 has a generally hemispherical shape that definesthe shape of the cavity 27. The inner surface 30 has an average diameterthat is less than that of the outer surface 29. Moreover, the innersurface 30 has an average diameter that is uniform for of the sizes ofthe intermediate component 14. In other words, regardless of the size ofthe intermediate component 14, the average diameter of the innercomponent 30 remains the same. As a consequence, if the diameter of theouter surface 29 is increased, then the thickness of the intermediatecomponent 14 increases.

The diameter of the inner surface 30 is preferably, but not necessarily,chosen such that the thickness of the smallest intermediate component 14is about 2-5 mm. Such thickness generally ensures the reliability of thecomponent for use during the trial reduction. In the exemplaryembodiment described herein, the intermediate component 14 isconstructed from acetal, which is available as Delrin™ from 3M Co.

The rim 32 further includes a plurality of substantially semi-circularprotrusions 34 that extend outward from the edge in which the outersurface 28 intersects with the edge 32. The protrusions 34 areconfigured to be received by the depressions 28 in the rim. When theintermediate portion 14 is seated within the outer shell 12, theprotrusions 34 are received into the depressions and help inhibitrotational movement of the intermediate portion 14 with respect to theouter shell 12. The intermediate component 14 further includes a bore 31that is configured to align with the threaded bore 24 of the outer shell12.

The inner component 16 is a rounded component having an interior cavity37 that includes an outer surface, not visible in FIG. 1, an innerbearing surface 38, and a substantially circular rim 40. At least aportion of the outer surface has a size and shape adapted to be receivedby the cavity 27 defined in the intermediate component 14. As willbecome apparent in the discussion of FIG. 4, a portion of the outersurface of the inner component 16 extends out of the cavity 27 and helpsdefine an interface to the femoral head. The interface is also definedby the circular rim 40 and the inner bearing surface 38. To this end,the inner surface 38 defines an interior cavity 37, which is configuredto receive one of a plurality of femoral heads, not shown.

More specifically, the inner bearing surface 38, has a plurality ofconfigurations, each adapted to receive one of a plurality of femoralheads, and further adapted to include other shape features that affectthe alignment and/or range of motion of the femoral head. Further detailregarding these features is provided below in connection with FIG. 2.

Regardless of the configuration of the bearing surface 38 of the innercomponent 16, the portion of the outer surface of the inner component 16that is disposed within the inner surface 30 of the intermediatecomponent 14 will have substantially a uniform average diameter. Inparticular, the average diameter of the outer surface of the innercomponent 16 will be substantially the same as the average diameter ofthe inner surface 30 of the intermediate component 14. As a consequence,both the inner surface 30 of the intermediate component 14 and the outersurface of the inner component 16 always fit together, regardless ofwhich configurations of intermediate component 14 and inner component 16are chosen.

As discussed above, the inner bearing surface 38 is selected to have aconfiguration that is suitable for the anatomy of the patient. Theconfiguration of the inner bearing surface is defined by its size(average diameter) and style (shape/alignment).

In particular, the inner bearing surface 38 will have one of a pluralityof sizes as measured by its average diameter. Preferably, the averagediameters range from about 22 mm to about 36 mm. Because the outerdiameter of the inner component 16 is constant and the inner diametervaries, the thickness of the inner component 16 will vary substantially,for example, from about 3 mm to about 10 mm.

In addition, the inner bearing surface 38 will have one a plurality ofliner styles. For example, as is known in the art, inner liners ofacetabular cups such as the inner component 16 may have a neutralbearing surface, a 10° bearing surface, a lipped bearing surface, or alaterized liner bearing surface. The inner bearing surface 38 shown inFIG. 1 is a standard neutral bearing surface. Selection among thevarious liner styles will depend on the anatomy of the patient, and istypically finally determined during trial reduction.

In the exemplary embodiment described herein, the inner component 16,like the intermediate component 14, is constructed from acetal, which isavailable as Delrin™ from 3M Co.

FIG. 2 shows in schematic form an exemplary modular acetabular trial kit100 in accordance with the present invention. The modular acetabular kit100 of FIG. 2 includes a plurality of outer shells 112 a-112 f, aplurality of intermediate components 114 a-114 f, and a plurality ofinner components or liners 116 a-116 m. The plurality of outer shells112 a-112 f may suitably have the general shape of the outer shell 12 ofFIG. 1. However, outer shells of other types that are typically employedin two-piece acetabular cups may be used. Regardless of the exact shape,each of the outer shells 112 a-112 f is defined by a specificcombination of an outer diameter (“OD”) and an inner diameter (“ID”).The OD varies so that the kit may accommodate differences in acetabulumsize in patients. The ID varies more or less as a function of the OD inorder to maintain a relatively consistent thickness of the outer shells112 a-112 f.

The plurality of intermediate components 114 a-114 f may suitably havethe general shape of the intermediate component 14 of FIG. 1. Regardlessof the exact shape, each of the intermediate components 114 a-114 f hasa specific combination of an OD and an ID. However, unlike the outershells 112 a-112 f, the IDs of the intermediate components 114 a-114 fare uniform in size. Nevertheless, the ODs of the intermediatecomponents 114 a-114 f vary such that each of the intermediatecomponents 114 a-114 f has an OD that is substantially the same as theID of one of the plurality of outer shells 112 a-112 f. Because the ODsof the intermediate components 114 a-114 f vary and the IDs are uniform,the thickness (defined as the OD−ID) is different for each of theintermediate components 114 a-114 f.

The plurality of inner components 116 a-116 m have the general shape ofthe inner component 16 of FIG. 1, but essentially include an outersurface portion having an OD and an inner bearing surface having one ofa plurality of configurations defined by an ID and a liner style. TheIDs of the inner components 116 a-116 m range from about 22 mm to 36 mm,and the liner styles include neutral, 10° lipped, and lateralized. Inthe exemplary embodiment described herein, thirteen configurations, eachincluding a unique combination of ID and liner style, are available. Ashort description of the various styles follows, although detailsregarding the inner liner styles would be known to those of ordinaryskill in the art.

The neutral liner style (e.g. inner components 116 a-116 d) has aneutral bearing surface, exemplified by the inner bearing surface 338 ofFIG. 3 a. The neutral liner style is concentrically aligned with theouter shell and is indicated in normal circumstances.

The 10° liner style (e.g. inner components 116 e-116 h) has an 10°offset bearing surface, exemplified by the inner bearing surface 438 ofFIG. 4 a. The 10° liner style provides a bearing surface that has anoffset angle to the outer shell. The 10° liner style is used to correctanteversion in the leg, and may be required if the outer shell isimplanted at an incorrect angle.

The lipped liner style (e.g. inner components 116 i-116 j) resembles theneutral liner style, except that one side of the liner extends out ofthe outer shell, forming a lip. The lipped liner style may be indicatedif separation of the femoral head from the acetabular cup is observedduring trial reduction.

The lateralized liner style resembles the neutral liner style exceptthat the inner bearing surface is eccentric, or offset laterally withrespect to the outer shell. The lateralized liner style may be indicatedif soft tissue laxity is present or if extra-articular impingement isobserved during trial reduction.

Referring again specifically to FIG. 2, the OD of each of the innercomponents 116 a-116 m is uniform, and is substantially the same as theID of each of the intermediate components. In the exemplary embodimentdescribed herein the OD of each of the inner components 116 a-116 m is42 mm. As discussed above, because the ODs of the inner components 116a-116 m are uniform and the IDs vary, the thickness of the innercomponents 116 a-116 m vary.

As shown in FIG. 2, the acetabular trial kit allows any of the outershells 112 a-112 f to be mated with any of the inner components 116a-116 m. The intermediate components 114 a-114 f provide an interfacebetween the outer shells 112 a-112 f and the inner components 116 a-116m to eliminate the need for thirteen different types of inner componentsfor each of the six outer component sizes. Moreover, the outer shells112 a-112 f, which can be made of a titanium alloy or stainless steel,are of relatively consistent thickness. As a consequence, a trialreduction may be performed using one or more of the inner components 116a-116 m even if the final acetabular outer shell is employed instead ofthe trial outer shell.

FIGS. 3 a-3 c and FIGS. 4 a-4 c show two different exemplary acetabulartrials 300 and 400 that may be formed from the kit 100 of FIG. 2. Theacetabular trial 300 of FIGS. 3 a, 3 b and 3 c includes an outer shell112 a from the kit 100 of FIG. 2 having an OD of 68 mm and an innercomponent 116 d having a 36 mm ID and a neutral liner style. Theacetabular trial 400 of FIGS. 4 a, 4 b and 4 c includes an outer shell112 f from the kit 100 of FIG. 2 having an OD of 78 mm and an innercomponent 116 e having a 22.225 mm and a 10° liner style.

Referring more specifically to the acetabular trial 300 of FIGS. 3 a, 3b, 3 c, the inner component 116 d is disposed within the intermediatecomponent 114 a, which in turn is disposed within the outer shell 112 a.The intermediate component 114 a has an OD of 52 mm, which correspondsto the ID of the outer shell 112 a. The intermediate component 114 afurther has an ID of 42 mm, which is the uniform ID of the intermediatecomponents 114 a-114 f of the kit 100. (See FIG. 2).

The intermediate component 114 a includes protrusions 334 that nestwithin corresponding depressions 328 in a rim 326 of the outer shell 112a. The protrusions 334 and the depressions 328 cooperate to inhibitrotation of the intermediate component 114 a with respect to the outershell 112 a.

The inner bearing surface 338 of the inner component 116 d is in theneutral style. In the neutral style of the acetabular trial 300, the rim340 of the inner component 116 d, the rim 332 of the intermediatecomponent 114 a and the rim 326 of the outer component 112 a all lay insubstantially parallel planes. As such, the style is “neutral”, meaningthat there is no angle of inclination similar to that of the rim of theinner component 116 e shown in FIG. 4 and discussed below.

The components 112 a, 114 a and 116 d are assembled and secured togetherusing a threaded fastener 350. The threaded fastener 350 includes athreaded end 352 that is received by the threaded bore 324 in the outershell 112 a. The threaded fastener 350 further includes a head 354defined by an annular shoulder 356 and a hollow cylinder 358 extendingupward therefrom. The annular shoulder 356 is configured to engage anannular ridge 360 in the bore 331 of the intermediate component 114 a.The hollow cylinder 358 is configured to engage an annular detent 362 inthe bore 342 of the inner component 116 d in a friction fit.

It can be readily appreciated that any of the inner components 116 a-116m can be used with the combination of the outer shell 112 a and theintermediate component 114 a. Thus, if during a trial reduction it islearned that the inner component 116 d does not provide an adequate fitor alignment, another of the inner components 116 a-116 m may besubstituted for the inner component 116 d.

Referring specifically to the acetabular trial 400 of FIGS. 4 a, 4 b and4 c, the inner component 116 e is disposed within the intermediatecomponent 114 f, which in turn is disposed within the outer shell 112 f.The intermediate component 114 f has an OD of 62 mm, which correspondsto the ID of the outer shell 112 f. The intermediate component 114 ffurther has an ID of 42 mm, which is the uniform ID of the intermediatecomponents 114 a-114 f of the kit 100. (See FIG. 2).

Apart from the difference in thickness and OD, the intermediatecomponent 114 f is substantially structurally the same as theintermediate component 114 a of FIG. 3. Specifically, the intermediatecomponent 114 f includes protrusions 434 that nest within correspondingdepressions 428 in a rim 426 of the outer shell 112 f. The protrusions434 and the depressions 428 cooperate to inhibit rotation of theintermediate component 114 f with respect to the outer shell 112 f.

The inner bearing surface 438 has a 10° phase change style. In the 10°phase change style of the acetabular trial 400, the rim 440 of the innercomponent 116 e is in a plane that is inclined with respect to theparallel planes in which the rim 432 of the intermediate component 114 fand the rim 426 of the outer component 112 f lie. As such, the style isnot neutral, but inclined by 10°.

The components 112 f, 114 f and 116 e are assembled and secured togetherusing a threaded fastener, not shown, in an analogous manner as thatdescribed above in connection with FIG. 3.

The exemplary acetabular trials 300 and 400 thus illustrate theflexibility of the kit 100. The acetabular trial 300 has a relativelylarge ID defined by its inner component 116 d and a relatively small ODdefined by its outer shell 112 a, while the acetabular trial 400 has arelatively small ID and a relatively large OD. The trials 300 and 400also illustrate how different styles (neutral, 10° lipped, andlateralized) may be used. Those of ordinary skill in the art couldreadily incorporate these and other styles into inner bearing componentsas desired.

In practice, the acetabular trial kit 100 of the present invention maybe used in either a total or partial hip replacement procedure in orderto provide an artificial bearing surface. FIGS. 5 a, 5 b and 5 cillustrate a surgical method for implanting an exemplary set ofcomponents from the kit 100 of FIG. 2.

Referring to FIG. 5 a, a reamer, not shown, is used to ream or otherwisecut the acetabulum 502 in order to form a hemispherically shaped cavity504 therein. The surgeon may then implant the trial outer shell 112 iinto the cavity 504, as illustrated by FIG. 5 b. The outer shell 112 imay be press fit or cemented into the cavity 504. The trial outer shell112 i is chosen based on the diameter of the cavity 504.

In a typical embodiment, the outer shell 112 i is implanted into thecavity 504 separately and then the intermediate component 114 i issecured to the outer shell 112 i in vivo. The intermediate component 114i is chosen based on the selection of the trial outer shell 112 i. Forexample, as shown in FIG. 2, each outer shell 112 i has a correspondingintermediate component 114 i with which it is used.

Thereafter, the surgeon selects a first trial inner component 116 j. Thesurgeon secures the first trial inner component 116 j to theintermediate component 114 i and both devices are affixed to the outershell 112 i in vivo as shown in FIG. 5 c. The first trial innercomponent 116 j may suitably be affixed to the intermediate component114 i external to the body and then both devices are affixed to theouter shell 112 i as a unit. However, in alternative embodiments, theintermediate component 114 i alone may be affixed to the outer shell 112i in vivo, and then the trial component 116 j would be affixed to theintermediate component 114 i in vivo.

The surgeon then performs a trial reduction. To perform the trialreduction, the femoral head, not shown, is inserted into the cavitydefined by the inner surface of the first trial inner component 116 j.If the trial reduction is successful, the trial components may beremoved and replaced with final implant components.

If, however, the trial reduction indicates a poor fit, poor alignment,or poor range of motion, then the first trial inner component 116 j isremoved from the intermediate component 114 i and is replaced with asecond trial inner component 116 k which has a different configuration.For example, if the trial reduction indicated a poor fit, then thesecond trial inner component 116 k may be selected such that is has adifferent size ID. If instead the trial reduction indicated pooralignment or poor range of motion but a good fit, then the second trialinner component 116 k may be selected such that it has a differentstyle, but the same ID. Once the second trial inner component 116 k issecured within the intermediate component 114 i, then another trialreduction is performed.

The replacement of the inner component may be repeated until the bestcombination of fit, alignment, and range of motion is achieved. Duringthe trial reduction, the surgeon tests the alignment of the femur andrange of motion. Suitable test methods are known in the art.

Once the appropriate inner component configuration is determined,corresponding final components may be implanted. In a preferred mode,the final outer shell, not shown, as a geometry substantially similar tothe outer shell 112 i, and the final inner liner, not shown, has ageometry that includes the outer diameter geometry of the intermediatecomponent 114 i and the inner diameter geometry of the trial inner linercomponent 116 k.

It will be appreciated that the above describe embodiments are merelyexemplary, and that those of ordinary skill in the art may readilydevise their own implementations and variations that incorporate theprinciples of the present invention and fall within the spirit and scopethereof.

For example, the broader concepts of the invention described hereinwould provide at least some benefits in other types of orthopaedicimplant systems, such as knees, shoulders or the like. In such devices,the components do not necessarily define substantially hemisphericalshapes.

1. An orthopaedic implant kit comprising: a plurality of outercomponents, each of at least two of the plurality of outer componentshaving (i) an outer surface geometry that is dimensioned differently incomparison to the outer surface geometry of the other of the at leasttwo of the plurality of outer components, and (ii) an inner surfacegeometry that is dimensioned differently in comparison to the innersurface geometry of the other of the at least two of the plurality ofouter components; a plurality of intermediate components, each of atleast two of the plurality of intermediate components having (i) anouter surface geometry that is dimensioned differently in comparison tothe outer surface geometry of the other of the at least two of theplurality of intermediate components, and (ii) an inner surface geometrythat is the same in comparison to the inner surface geometry of theother of the at least two of the plurality of intermediate components;and a plurality of inner components, each of at least two of theplurality of inner components having (i) an outer surface geometry thatis dimensioned the same in comparison to the outer surface geometry ofthe other of the at least two of the plurality of inner components, and(ii) an inner surface geometry that is dimensioned differently incomparison to the inner surface geometry of the other of the at leasttwo of the plurality of inner components.
 2. The orthopaedic implant kitof claim 1, wherein each of the plurality of outer components has asubstantially hemispherical shape.
 3. The orthopaedic implant kit ofclaim 1, wherein each of the plurality of outer components comprises anacetabular outer shell.
 4. The orthopaedic implant kit of claim 1,further comprising a rotatable fastener for coupling one of theplurality of outer components to one of the plurality of intermediatecomponents.
 5. The orthopaedic implant kit of claim 1, wherein each ofthe plurality of outer components has an outer surface configured toengage bone tissue.
 6. The orthopaedic implant kit of claim 1, whereineach of the plurality of bearing components has an inner surfaceconfigured to mate with a complementary configured bearing member. 7.The orthopaedic implant kit of claim 6, wherein said complementaryconfigured bearing member is a bearing member of a femoral head.